Combined phase and time-of-flight measurement

Abstract

Systems and methods of measuring distance between two wireless devices by combining phase shift and time-of-flight measurements. A first wireless devices sends a first packet to the second wireless device. After receiving the first packet, the second wireless device sending to the first wireless device a second packet. After sending the second packet, the second wireless device sends a first continuous wave signal to the first wireless device. After receiving the first continuous wave signal, the first wireless device sends to the second wireless device a second continuous wave signal. The first wireless device then calculates a time-of-flight measurement based on a time between the first wireless device sending the first packet and receiving the second packet, and calculates a second measurement based on a phase shift of the first continuous wave signal and the second continuous wave signal, and combines the two measurements.

What is claimed is: 
     
         1 . An electronic device comprising:
 a transceiver; and   a processor configured to:
 provide, via the transceiver, a first packet to a wireless device; 
 receive, via the transceiver, a second packet from the wireless device; 
 receive, via the transceiver, a first continuous wave signal from the wireless device; 
 determine a first measurement of a distance to the wireless device based on a time between the first packet and the second packet; 
 determine a second measurement of the distance to the wireless device based on a first phase associated with the first continuous wave signal; and 
 determine a third measurement of the distance to the wireless device based on the first and second measurements. 
   
     
     
         2 . The electronic device of  claim 1 , wherein the processor is configured to provide, via the transceiver, a second continuous wave signal to the wireless device. 
     
     
         3 . The electronic device of  claim 2 , wherein the first phase is based on a second phase associated with the second continuous wave signal. 
     
     
         4 . The electronic device of  claim 3 , wherein a first frequency of the first continuous wave signal is based on a second frequency of the second continuous wave signal. 
     
     
         5 . The electronic device of  claim 2 , wherein the processor is configured to:
 provide the first packet and the second continuous wave signal during a first transmission phase; and   after the first transmission phase, transition to a first reception phase to receive the second packet and the first continuous wave signal.   
     
     
         6 . The electronic device of  claim 5 , wherein the processor is configured to provide the second continuous wave signal after providing the first packet. 
     
     
         7 . The electronic device of  claim 2 , wherein the processor is configured to provide the second continuous wave signal after providing the first packet. 
     
     
         8 . The electronic device of  claim 7 , wherein the processor is configured to:
 provide the first packet during a first transmission phase;   receive the second packet during a first reception phase;   provide the second continuous wave signal comprises during a second transmission phase; and   receive the first continuous wave signal during a second reception phase.   
     
     
         9 . The electronic device of  claim 8 , wherein the processor is configured to:
 transition from the first transmission phase to the first reception phase;   after transitioning from the first transmission phase to the first reception phase, transition from the first reception phase to the second transmission phase; and   after transitioning from the first reception phase to the second transmission phase, transition from the second transmission phase to the second reception phase.   
     
     
         10 . The electronic device of  claim 7 , wherein the processor is configured to:
 provide the first packet during a first transmission phase;   receive the second packet during a first reception phase;   provide the second continuous wave signal during a second transmission phase; and   receive the first continuous wave signal during the first reception phase.   
     
     
         11 . The electronic device of  claim 2 , wherein a second phase associated with the second continuous wave signal is based on the first phase. 
     
     
         12 . The electronic device of  claim 11 , wherein a second frequency of the second continuous wave signal is based on a first frequency of the first continuous wave signal. 
     
     
         13 . The electronic device of  claim 1 , further comprising an oscillator, wherein the processor is configured to:
 provide the first packet during a first transmission phase;   receive the second packet during a first reception phase; and   keep the oscillator locked to a first frequency during a transition from the first transmission phase to the first reception phase.   
     
     
         14 . The electronic device of  claim 1 , wherein the transceiver comprises a transmitter comprising a first amplifier, and a receiver comprising a second amplifier, and wherein the processor is configured to:
 provide the first packet during a first transmission phase;   receive the second packet during a first reception phase; and   during a transition from the first transmission phase to the first reception phase:
 power down the first amplifier, and 
 power up the second amplifier. 
   
     
     
         15 . The electronic device of  claim 1 , wherein determining the third measurement comprises averaging the first and second measurements. 
     
     
         16 . The electronic device of  claim 1 , wherein determining the third measurement comprises performing a weighted average of the first and second measurements. 
     
     
         17 . The electronic device of  claim 1 , wherein the first packet is a synchronization word packet. 
     
     
         18 . The electronic device of  claim 17 , wherein the second packet is an acknowledge packet. 
     
     
         19 . The electronic device of  claim 1 , wherein the electronic device is a vehicle. 
     
     
         20 . The electronic device of  claim 19 , wherein the processor is configured to perform an unlock action in response to the third measurement being lower than a predetermined threshold.